This invention relates to a semiconductor device washing apparatus and a method of washing the semiconductor device after a Chemical Mechanical Polishing (CMP) process.
Conventionally, irregularities are often formed on a surface of a semiconductor device having a laminate structure in a step of manufacturing the semiconductor device. The surface having the irregularities is flattened by the use of the known CMP (Chemical Mechanical Polishing) process.
This polishing process is generally carried out by using solution containing dense polishing particles (for example, silica particles, alumina particles) during the CPM process. These particles must be almost completely removed from a wafer surface after the CMP process to keep reliability of an electronic device and a desired cleaning degree of a manufacture line.
In particular, when a hydrophobic film, such as, a silicon nitride film and a polysilicon film, is polished, it is difficult to remove particles which are left on the hydrophobic surface in comparison with a hydrophilic surface. Therefore, a washing method of effectively removing the particles has been required.
A brush scrub method using a sheet-fed type spin washing apparatus is generally used as the method of removing the particles which are left on the wafer after the CMP process.
For example, the spin washing apparatus includes a roll blush 12, an exhaust nozzle 13, a chemical liquid tank 15, and a pure water exhaust nozzle 14, as illustrated in FIG. 1.
In this event, the roll brush 12 removes particles which are left on a wafer 11. In the exhaust nozzle 13, an exhaust hole is opposite to the wafer 11. Further, chemical liquid is contained in the chemical liquid tank 15. The chemical liquid is injected or sprayed from the exhaust hole towards or onto the wafer 11. Moreover, pure water is injected or sprayed from an exhaust hole of the pure water exhaust nozzle 14 towards or onto the wafer 11.
In the above-mentioned spin washing apparatus, the roll brush 12 is contacted with the wafer 11. The washing water is supplied from the chemical liquid tank 15 towards the wafer 11 through the exhaust nozzle 13.
Under this circumstance, the wafer 11 is washed by pure water which is injected from the pure water exhaust nozzle 14 on the condition that the wafer 11 and the roll brush 12 are rotated.
In this case, dilution ammonia solution (I. J. Malik et al.: MRS. Symp. Proc. Vol. 386, p.109 (1995)) or dilution hydrofluoric acid solution is used as the washing water other than the pure water. However, these solutions are not effective for washing the above-mentioned hydrophobic surface.
In contrast, a report has been made about an example in which hydrophobic property is improved to enhance the removing effect (or performance) by adding detergent during the CMP process and the subsequent washing process in the 57th prof. (p. 637, 8p-L-7) of [The Japan Society of Applied Physics]. Herein, it is to be noted that a main component of the washing solution may be uncertain in the above-mentioned report.
Further, disclosure has been made about a conventional example for obtaining a hydrophilic surface by adding alcohol liquid during the CMP process in Japanese Unexamined Patent Publication (JP-A) No. Hei. 9-277172.
However, the ammonia solution or the dilution hydrofluoric acid solution does not have capability for obtaining the hydrophilic surface. Consequently, it is not sufficiently effective to wash the hydrophobic surface.
On the other hand, although the ammonia water containing the detergent is effective, there is the following problem. Namely, it is easy that high-polymer organic substance constituting the detergent is left on the wafer after the washing process. Consequently, a washing step for removing the organic substance further becomes necessary.
Further, if a proper liquid wasting process is not performed for the detergent, the detergent gives an adverse effect for the environment. In consequence, it is necessary to prepare an expensive processing facility to carry out the proper process.
With respect to the example for adding the alcohol during the CMP process, the alcohol serves as a first washing liquid in a polishing apparatus for performing the CMP process. However, the alcohol does not serve as a final washing liquid for the subsequent step of depositing a film.
In general, the washing process in the polishing apparatus accompanies with contaminants inside the apparatus. Consequently, high cleaning washing can not be performed. As a result, an additional polishing apparatus is required to be arranged independently of the subsequent washing apparatus.
Further, when the hydrophobic surface, such as, the silicon nitride film and the polysilicon film, is exposed after the CPM process, it is difficult to remove the particles which are left on the hydrohobic surface as compared to the hydrophilic surface.
Therefore, a washing method for effectively removing the particles has been required.